The main objective of this project is to describe the separate and combined effects of in-utero tobacco smoke (UTS) exposure and post-natal environmental tobacco smoke (ETS) exposure upon lung function and respiratory health in a population followed longitudinally from their mothers' pregnancy until age five years. Women will be enrolled in early to mid-pregnancy and their exposure to tobacco smoke (active and passive) will be studied in detail during the pregnancy using historical data, cotinine levels and alveolar carbon monoxide (CO) monitoring. The UTS exposure of the infants will then be related to their lung function (infant partial expiratory flow-volume maneuvers and lung volume) measured at two weeks of age and then three subsequent times over the next 18 months, to cord blood IgE, and to histopathologic alterations in the placenta and umbilical cord. Respiratory health (symptom and illness) will be tracked using telephone interview, questionnaires, and clinic record review over the same time period. Post-natal ETS exposure will be quantified in both infants and mothers in detail over the first 18 months as well, including questionnaire and urine cotinine determinations. From 18 months until three years respiratory health and ETS exposure data will be obtained by questionnaires administered at six month intervals. From age three to five, the subjects will be seen annually and have lung function measured (lung volumes, partial expiratory flow-volume maneuvers), ETS exposure estimated (questionnaire and urine/salivary cotinine), and interval respiratory health quantified (questionnaire). In addition, at age five, full spirometry (maximal expiratory flow-volume maneuver) and bronchodilator response measures will be attempted. Multiple longitudinal analyses are described in detail in the proposal. The focus is upon modelling the longitudinal growth and development of the lung from birth until five years of age and then describing the impact of UTS/ETS exposure upon this process. Detailed respiratory health data will then be related to both lung function and smoke exposure data. This research group will then be able to combine this information with a pre-existing extensive study of lung function and related factors in children from age five to seventeen to identify mechanisms by which passive exposure to cigarette smoke alters respiratory health and may lead to chronic obstructive airway disease.